I suppose I will be the somewhat odd cat out here; but, I don't find the vertical stack to be the big thing that apparently most others do.
When I gig my 212 + 112 stack, I do stack them. Yes, it sounds great:
However, when I acquired a 2nd AE212, I had several exchanges with other TB'ers (wish I could remember without searching which of you provided the input); and after a lot of experimentation with various arrangements arrived at the following setup as optimal for the sound I like:
I spent a lot of time listening carefully to several configurations including vertical stacking, but ultimately find this shallow V a lot more pleasing; and it is far more stable on some of the nasty stages I get to gig. LOL.
The dispersion thing is interesting; but to me, in terms of the slot in the mix the bass provides, it's a bit subtle. The frequencies that comb the most perceptively tend to be the higher frequencies, and you definitely can hear the effect walking around a big room on a long cord when the cabs are simply side by side. To me, if this causes the bass to "not be heard," then there are other problems with the bass tone shaping. I do agree that the stack or the shallow V keep the sound field projecting from the cabs more uniform.
Anyhow, if space allows, I go shallow V. If stage space is tight, then I stack. I'm only 6'0"; so just a shortie. My $0.019.